This document summarizes estimates of change in mature individuals over time for Pacific salmon Designatable Unit (DU) and associated probable COSEWIC status designation. Data sources are detailed here and all code to reproduce the analyses in this document is here. These materials are solely intended to support the Marine Fishes sub-committee of COSEWIC in identifying high priority DUs for COSEWIC to consider when conducting formal status assessments.
Initial thoughts on potential decision nodes in the prioritization process.
Have DUs been formally defined by COSEWIC? Chinook, sockeye, and coho salmon DUs have been defined (reports available here), formal pink and chum DU identification is in progress. If yes then proceed.
Is information on mature individuals over time available at the DU scale? If yes then proceed.
Has DU been previously assessed by COSEWIC? If yes then consider a re-assessment, otherwise proceed.
What is the DUs probable designation based on percentage change in mature individuals over past three generations? If special concern, threatened or endangered then proceed.
Are there spatial considerations? Are there commonalities in threats, designations, and/or data landscape at a regional scale that suggest a group of DUs should be bundled together?
Figure 1. Probable status of previously unassesed Pacific salmon DUs based on rate of change in mature individuals over most recent three generations.
We will also use the MetricsCOSEWIC package to fit Bayesian estimates of the probability of population decline, then plot posteriors to see the distribution of declines. Thresholds for population decline based on category A2, where 50 and 30 percent reductions correspond to endangered and threatened status, respectively. we’ll use 30, 50, and 70 % reductions as thresholds for least concern, threatened, and endangered for now.